Calcium, magnesium, iron additives

Combination calcium (Ca), magnesium (Mg) and iron (Fe) additives are used
to help overcome or prevent the deficiency of these elements. The
deficiency of these 3 elements can cause common symptoms such as
blossom-end-rot (death of the end part of fruit), upward leaf curl,
withered flower/fruit set, interveinal chlorosis and the death of
terminal buds and root tips.

If the above mentioned symptoms are present, be sure to check pH and
humidity levels. Excessive pH can cause both calcium and iron to become
insoluble. Excessive humidity restricts the distribution (“translocation”)
of nutrients throughout the plant and is a common cause of calcium
deficiency.

Avoid using this additive with excessively hard make-up water because it
can cause the build-up of white "scale". This can result in dripper
blockage and a reduction in the amount of available sulfate - an essential
plant nutrient.